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2sp to turbo700 swap

6K views 19 replies 4 participants last post by  lovebohn 
#1 ·
Hi guys I have a 2sp and would like to change it to turbo 700 when I put my 327 back in my impala what would I need to change and swap over.

does the cross member need to be change and can you buy one made
also tail shift does that need to be made small cause the turbo 700 is bigger I see you can buy the console parts for the shifter so that all good there.

thanks.
 
#2 ·
Depends upon the year of your car.

The 700R4 is physically longer than the PowerGlide so you will need to cut down the overall length of your drive shaft. The mounting point that the tranny bolts up to is also located further back that the PG, so depending upon your car body you either move the old cross-member back and drill new bolt holes in the frame rails or buy a fabricated transmission cross-member to fit your 700R4 in your car.

The transmission uses metric nut and bolts as well as it's tube size so you will need an adapter to splice the two hydraulic lines together (this assuming your PowerGllide isn't an earlier air cooled one without hydraulic lines going to your radiator). The gear selector linkage works as far as the bell crank under the car. It needs to be lengthened if you expect to select all of the gears manually.

Otherwise it will work as is giving you just P N and Dive. To access OD you have to either wire in a switch to flip it into OD, or use a hydraulic switch that will toggle the OD when it sees a preset pressure in high gear. You tie into the brake pedal switch to turn OD off.

The new lock-up torque converter bolts to a metric flex plate that is drilled for a smaller one piece rear main seal so you will need to buy an aftermarket SFI approved flex plate to bolt the new torque converter to your older two piece rear main seal crank flange.

Big Dave
 
#3 ·
What year of Impala ????OK I'll try and help as I am just putting the finishing touches on this swap in my 63 .:beers: .AS Dave said it is longer trans cross member will need moved back I made my own, various vendors have a complete kit or just the cross member for this swap. I like to fab my own stuff when I can , trans cooling lines were a direct swap just a little bending , 700 has a different tail shaft yoke you need 1 for your trans either a 27 or 20 spline depending on what year trans you get. There is a seam (lip) where your floor board meets the firewall it needs trimmed alittle where the dipstick comes up it will interfere and rub . Depending on the year of trans you will need to swap your speedometer gears over to manual, the newer ones went to electric . Shift linkage will need altered to get the gears to work properly. Allso the driveshaft will need cut about 3" I am going to a 1 piece driveshaft and eliminate the center carrier another option to look at. And then you need the TV cable which is the most important part when your ready to drive set it right or smoke your trans . Like I said there are some vendors out there that offer a complete kit for this which would save time but I don't have the funds $$ for this so I fabbed my own stuff up .Good Luck :thumbsup:
 
#5 ·
It helps you as the there is more room under the car and between the frame rails. No two piece drive shaft to worry about or small 20 spine PowerGlide output shaft. Your PowerGlide uses the same output yoke as the 700R4. I'm sorry I forgot to mention the TV cable all together. It is important to adjust it correctly as it controls the line pressure applied to the clutches and drums. Out of adjustment and everything burns up in a mater of minutes.

There are actual conversion kits put together by many vendors that will have everything you need with instructions in one box.

Ecklers lists all of the parts starting with a cross-member:

http://www.lategreatchevy.com/full-...transmission-hardtop-and-sedan-1965-1975.html

Chevy lock-up pressure switch, 700R4 Transmission:

http://www.lategreatchevy.com/full-size-chevy-pressure-switch-700r4-transmission-1958-1972.html

Turbo Hydra-Matic 700R4 (TH700R4), With Stock Lock-up Torque Converter:

http://www.lategreatchevy.com/full-...-th700r4-with-torque-converter-1958-1972.html

Powerglide To 4-Speed Automatic Transmission Shifter Conversion Kit:

http://www.lategreatchevy.com/full-...mission-shifter-conversion-kit-1965-1967.html

Chevy Transmission To Radiator Metric O-Ring Cooling Line Adapters:

http://www.lategreatchevy.com/full-...radiator-cooling-line-fittings-1958-1972.html

These may not be needed it depends upon the year of the donor transmission. The 700R4 from it's introduction in 1984 was improved annually. The yearly changes made the transmission stronger every year. The newer the better up to the introduction of the 4L60e transmission which is a 700R4 renamed and more importantly computer controlled instead of using the hydraulics in the valve body to shift the tranny. Even some 4L65e parts are still backward compatible with an older 700R4 and high performance transmission shops will rebuild a 700R4 using those parts (even so the Sun Shell is still weak and will snap off if any serious torque such as from a 502 cube BBC is applied).

Detent Bracket, For Cars With Carburetor

http://www.lategreatchevy.com/full-size-chevy-detent-bracket-for-cars-with-carburetor-1958-1972.html



Big Dave
 
#8 ·
That one has an electric sending unit.

The way I did it for one car was to buy a $700 electric motor that takes the digital input and syncs a DC motor to the correct RPM by varying the voltage to the motor. Basically the missing computer is in the case with the motor bolted under the car along with the drive motor.

Another cheaper possibility that I used after that fiasco was to buy an electric speedometer to match my Tach from Auto-meter (Both had the black five inch Sport Comp face for day light driving). This worked out fine for me as I place all of the important gauges on top of the dash in my line of sight due to my size (my head is touching the head liner and my eye line is just below the sun visors so I get the advantage of built in sun glasses due to the extra dark tint at the top of the windscreen as I drive).

If you are not 6'-6'' then you might have to build a custom dash to place your gauges in to the dash which is how a mod on another board did it with his Nova and if you had a Camaro there are aftermarket dashes sold to accept Auto-meter gauges. With an Impala you are on your own; and you will need to go the custom route. This will be a pain in most years as the gauges in the original dash are linear instead of round to simulate a sports car.

The proper solution is to find and earlier year transmission that has a mechanical gear set and buy the tail housing off of it. Then buy a new set of speedometer gears to match your rear end ratio from these guys who also sell tail housings ready to go (all cleaned up used ones). These guys web site also has a calculator that you punch in your rear gear ratio and they tell you the proper colored gears to buy, or you can call them on the phone and talk to them if you don't mind staying up all night as they are very helpful even if they half way around the world from where you live.

http://www.transmissioncenter.net

Big Dave
 
#10 ·
Don't know which switch you are talking about. The 700R4 and the 200R4 both use a pressure switch that measures the hydraulic line pressure that feeds the OD piston to engage the clutch that limits the slip in the torque converter. You need to install a second wire to your brake light switch to disengage the lock up feature whenever you try and stop the car.

The valve body is a just collection of pressure switches that controls the transmission based upon gear selector position, governor weights and springs as well as check balls (one way valves) to control the transmissions operation instead of a computer. So I am not sure which pressure valve you are talking about. I'm no transmission guy I have to get the Service manual out to rebuild one, though I have done it several times (they are not that complex to repair just requiring three special tools that cost about the same as you would pay someone else in labor to fix yours).

Big Dave
 
#14 ·
Hi guys I have done the swap and everything worked out ok just need to get the drive shaft made
but can any one tell me if you can buy a shaft/linkage rod for the t-bar to select gears or any picture of one so I can see the bend
so I can make one. cheers
 
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